This invention relates in general to nuclear reactor core construction and more particularly to a nuclear reactor core stabilizing arrangement whereby fuel elements making up the core are pressed together and thereby stabilized against vibration induced by coolant flow through the core or by externally applied forces, such as seismic or other vibration induced forces.
In reactor cores having a plurality of elongated fuel assemblies positioned together in adjacent, laterally spaced-apart relation to one another to form a compact group, there generally exist clearance gaps of somewhat differing dimensions between adjacent fuel assemblies. This presents a problem under seismic and dynamic loading conditions, since the assemblies, with their high long column slenderness ratio can be easily set vibrating and such vibration can cause them to slam together with high impact loads, and the consequent hazard of breakage. To withstand such impact, canned fuel assemblies were used in the prior art.
The invention provides a core stabilizing arrangement whereby the fuel assemblies within the core are passed together at the mid-point of their span by actuators arranged in a pattern laterally surrounding the core. These actuators have platens positioned for contact with respective assemblies positioned about the periphery of the core. Consequently, the clearance between adjacent assemblies is reduced and the core assembly is firmly compacted to resist vibration, and to minimize the amplitude of any vibration that does occur. With the invention, it is therefore permissible to use less expensive canless fuel assemblies without sacrificing core integrity.
According to a preferred embodiment of the invention, the actuators are operated by input forces induced and applied by the emplacement of an upper grid structure that serves, together with a lower grid structure, to hold and retain the fuel assemblies in their intended parallel alignment. These input forces are directed substantially parallel to the longitudinal axis of the fuel assemblies, whereas the output forces exerted by the actuator platens against the fuel assemblies are directed in a substantially common plane perpendicular to these same axes.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawing and descriptive matter in which there is illustrated and described a preferred embodiment of the invention .